The invention relates to a driving authorization system having an electronic immobilizer function.
In conventional driving authorization systems it is possible to bypass an electronic immobilizer function by exchanging components, for example control units which are involved in the driving authorization system. For this reason, in order to increase security, an electronic immobilizer function can be coupled mechatronically to a sensor system or actuator system which is difficult to access on the internal combustion engine.
German patent document DE 43 36 212 C2 discloses a pickup arrangement for detecting cylinders in an internal combustion engine. For the purpose of detecting a defined position of a crankshaft in the internal combustion engine, the system includes a pickup disc, a reference mark which is arranged on the pickup disc, a sensor which is assigned to the pickup disc and a control device which evaluates the signal of the sensor. The reference mark characterizes a predefined position of the crankshaft which is assigned to the reference mark. In order to encode the internal combustion engine, the reference mark is assigned to a crankshaft position which is specific to the internal combustion engine.
Germany patent document DE 100 06 300 C2 describes an immobilizer for a vehicle which is driven by an internal combustion engine with an ignition signal transmitter coil which interacts with a pickup disc which is coupled to the crankshaft of the engine. The immobilizer comprises a circuit arrangement has (a circuit breaker or a short circuit switch) and a circuit activation circuit which closes the circuit breaker and opens the short circuit switch if it receives a predefined signal. It is embodied as an undetachable circuit unit with the ignition signal transmitter coil.
U.S. Pat. No. 5,570,016 discloses a method and apparatus for detecting the angular position of a crankshaft, which permit a rapid engine start. A combination of a pickup wheel and a sensor generates an analog signal that is converted into a digital output signal with 24 bits representing a 360° rotation of the crankshaft. Each bit represents a specific angular position of the crankshaft and in each case six successive bits of the repeating digital output sequence of 24 bits form a unique pattern. By monitoring the first six generated bits during a switch on process, which corresponds to a 90° rotation of the crankshaft, the angular position of the crankshaft can then be determined, permitting faster starting of the engine.
U.S. Pat. No. 5,615,649 discloses an engine security system with a security component that is adapted to receive a sequence of timing pulses generated as a function of the engine speed. After an enable code has been received from the timing pulse sequence, the security component generates an ignition pulse sequence which is synchronized with the engine speed. The ignition pulse sequence is applied to the ignition system of the engine in order to generate ignition sparks. The pulses of the timing pulse sequence occur at various times compared to the pulses of the ignition pulse sequence, and contain an encrypted identity code.
One object of the invention is to provide a driving authorization system having an electronic immobilizer function which is connectable to a vehicle assembly by a mechatronic connection, thereby providing improved protection against theft.
This and other objects and advantages are achieved by the driving authorization system according to the invention, in which a pickup wheel arranged on a rotary shaft has a predefined number of teeth are arranged along its circumference by means of encoding. The teeth generate an encoded rotational speed signal which is picked up by a rotary shaft sensor and can be decoded by a vehicle control unit in order to acquire information about the position and/or rotational speed of the rotary shaft. The vehicle control unit enables the electronic immobilizer function only after successful decoding of the encoded rotational speed signal. A synchronization time for detecting a specific position of the rotary shaft is part of the encoded rotational speed signal. Thus, without successfully decoding the encoded rotational speed signal, the vehicle control unit cannot synchronize the rotary shaft position and an associated vehicle system; for example it cannot synchronize a crankshaft position with injection times of an injection system.
By including the specific synchronization time in the encoding of the pickup wheel, attempts at manipulation are made considerably more difficult. The synchronization time can be used, for example, for synchronizing an internal combustion engine (i.e., for detecting a top dead center of a first cylinder). In this way, in contrast to conventional pickup wheels which have a corresponding visible marking (for example, a gap), an assignment of a specific rotary position of the rotary shaft to functions of an associated vehicle system can no longer be detected. As a result, it is no longer possible, for example, to assign the crankshaft position and the top dead center of the first cylinder from the outside without decoding.
In addition, synchronization of the rotary shaft with the associated vehicle system can occur only given knowledge of the encoding of the pickup wheel. Since the pickup wheel which is encoded mechanically by the distribution of teeth, and has the purpose of sensing the rotational speed, cannot be manipulated without considerable expenditure of materials and time, protection against theft is advantageously improved. In addition, the electronic immobilizer function of the driving authorization system is advantageously coupled to the associated vehicle assembly, for example to an internal combustion engine and/or to an automatic transmission, via the mechanically encoded pickup wheel.
In one advantageous development of the driving authorization system, the encoding along the circumference of the pickup wheel is divided into a predefinable number of segments which can each be unambiguously detected. Such encoding advantageously permits very rapid synchronization of the rotary shaft with the associated vehicle system, since less than one complete rotation of the rotary shaft is sufficient for synchronization. The speed of the synchronization is dependent on the size and number of the segments and can be increased by a relatively large number of segments or by relatively small segments.
In one embodiment of the driving authorization system according to the invention, at least two pickup wheels which are arranged on various rotary shafts can be evaluated by the associated vehicle control units in order to carry out mutual authentication. Encoding information and decoding information from various pickup wheels can be exchanged between two different vehicle control units for the purpose of mutual authentication in, for example, encrypted form via an electronic bus system. As a result, the decoding algorithms which are matched to the mechanical encoding of the associated pickup wheels can advantageously be mutually exchanged, monitored and, where necessary completed, so that theft protection is improved further.
In a further embodiment of the driving authorization system according to the invention, a pickup wheel for sensing the position and/or rotational speed of an associated rotary shaft can be arranged, for example, on a crankshaft and/or on at least one rotary shaft in an automatic transmission. A pickup wheel which is arranged on the crankshaft transmits the sensed position and/or rotational speed of the crankshaft to, for example, a vehicle control unit which is embodied as an engine control unit. A pickup wheel which is arranged on at least one rotary shaft in the automatic transmission transmits the sensed position and/or rotational speed of the associated pickup shaft to, for example, a vehicle control unit in the form of a transmission control unit. This has the advantage that even exchanging the internal combustion engine and/or the automatic transmission as an attempt at manipulation will not allow the respective vehicle to be used without authorization.
In a further embodiment of the driving authorization system according to the invention, the associated vehicle control unit decodes the encoded rotational speed signal which is picked up by the rotary shaft sensor and transmitted, with a decoding algorithm which can be enabled and activated by an authorized authentication element. As a result, the decoding algorithm which is matched to the mechanical encoding of the pickup wheel can advantageously be enabled only by an authentication element which is assigned to the vehicle. As a result protection against theft is enhanced.
In a further embodiment of the driving authorization system according to the invention, an enable signal for the decoding algorithm in the respective vehicle control unit is generated by a vehicle control unit which is embodied as an electronic ignition lock, after successful authentication. For the purpose of authentication, the electronic ignition lock communicates with the portable authentication element via a communication link. The enable signal which is generated in the electronic ignition lock can be transmitted in encoded form to the engine control unit via a data bus and decoded again by the engine control unit in order to enable the decoding algorithm. As a result, it is possible to implement a two-stage driving authorization checking system which electronically checks the authentication in a first stage and, in a second stage, checks the mechanically encoded coupling of the electronic immobilizer function to the corresponding vehicle assembly, such as the internal combustion engine and/or the automatic transmission.
In addition, information can be transmitted from at least one other vehicle control unit and/or from the authentication element to the vehicle control unit, which uses such information to decode the encoded rotational speed signal of an associated pickup wheel. This advantageously permits the necessary keys for decoding the mechanically encoded pickup wheels to be distributed to the entire electronic implementation of the immobilizer function in the vehicle and in the portable authentication element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.